A power converter device configured to covert alternating-current power into isolated direct-current power is used as a direct-current power supply for communications, for example. In general, this power converter device is a two-stage converter including a non-isolated power factor improvement circuit and a high frequency isolated DC-DC converter. Meanwhile, there is also disclosed a power converter device simplified in a circuit configuration in which a one-stage converter causes the alternating-current power to flow intermittently at high frequency and converts the alternating-current into the direct-current power.
FIG. 1 is a circuit diagram showing an example of a conventional AC-DC converter device disclosed in Japanese Patent Application Publication No. 2002-233155. The AC-DC converter device shown in FIG. 1 is a one-stage conversion high frequency isolated PWM rectifier, in which a series circuit formed of a bidirectional switch Q10 and a first primary winding 3a of a transformer 3 is connected between an alternating-current terminal (R phase) 2a and an alternating-current terminal (T phase) 2c of a three-phase alternating-current power supply 1. A series circuit formed of a bidirectional switch Q20 and a second primary winding 3b of the transformer 3 is connected between an alternating-current terminal (S phase) 2b and the alternating-current terminal 2a of the three-phase alternating-current power supply 1. A series circuit formed of a bidirectional switch Q30 and a third primary winding 3c of the transformer 3 is connected between the alternating-current terminal 2c and the alternating-current terminal 2b of the three-phase alternating-current power supply 1.
The bidirectional switch Q10 is formed of a series circuit including an insulated gate bipolar transistor (IGBT) Q11 and an IGBT Q12. The bidirectional switch Q20 is formed of a series circuit including an IGBT Q21 and an IGBT Q22. The bidirectional switch Q30 is formed of a series circuit including an IGBT Q31 and an IGBT Q32.
An anode of a direct-current power supply 11a is connected to a cathode of a direct-current power supply 10a, and an anode of the direct-current power supply 10a is connected to gates of the IGBTs Q11 and Q12 via a switch Sa1 in a gate drive circuit 12a. A cathode of the direct-current power supply 11a is connected to the gates of the IGBTs Q11 and Q12 via a switch Sa2 in the gate drive circuit 12a. The cathode of the direct-current power supply 10a and the anode of the direct-current power supply 11a are connected to emitters of the IGBTs Q11 and Q12.
An anode of a direct-current power supply 11b is connected to a cathode of a direct-current power supply 10b, and an anode of the direct-current power supply 10b is connected to gates of the IGBTs Q21 and Q22 via a switch Sb1 in a gate drive circuit 12b. A cathode of the direct-current power supply 11b is connected to the gates of the IGBTs Q21 and Q22 via a switch Sb2 in the gate drive circuit 12b. The cathode of the direct-current power supply 10b and the anode of the direct-current power supply 11b are connected to emitters of the IGBTs Q21 and Q22.
An anode of a direct-current power supply 11c is connected to a cathode of a direct-current power supply 10c, and an anode of the direct-current power supply 10c is connected to gates of the IGBTs Q31 and Q32 via a switch Sc1 in a gate drive circuit 12c. A cathode of the direct-current power supply 11c is connected to the gates of the IGBTs Q31 and Q32 via a switch Sc2 in the gate drive circuit 12c. The cathode of the direct-current power supply 10c and the anode of the direct-current power supply 11c are connected to emitters of the IGBTs Q31 and Q32.
A rectifier 4 rectifies a high-frequency voltage generated on a secondary winding 3d of the transformer 3. A series circuit formed of a smoothing reactor 5 and a smoothing capacitor 8 is connected between two terminals of the rectifier 4. A load 7 is connected to two terminals of the smoothing capacitor 8.
In the thus configured conventional AC-DC converter device shown in FIG. 1, the alternating-current power is inputted from the three-phase alternating-current power supply 1 at a commercial frequency to the bidirectional switches Q10, Q20, and Q30 as well as the primary windings 3a to 3c. 
The gate drive circuits 12a to 12c turn the switches Sa1, Sb1, and Sc1 on by use of a control signal from an unillustrated control circuit and turn the bidirectional switches Q10, Q20, and Q30 on by applying anode voltages from the direct-current power supplies 10a to 10c to points between the gates and the emitters of the bidirectional switches Q10, Q20, and Q30. Meanwhile, the gate drive circuits 12a to 12c turn the switches Sa2, Sb2, and Sc2 on and turn the bidirectional switches Q10, Q20, and Q30 off by applying cathode voltages from the direct-current power supplies 11a to 11c. 
Specifically, the alternating-current power from the three-phase alternating-current power supply 1 is subjected to high frequency switching by use of the bidirectional switches Q10, Q20, and Q30 whereby a high-frequency voltage having a higher frequency than the commercial frequency is generated on the primary windings 3a to 3c and the secondary winding 3d of the transformer 3. This high-frequency voltage is rectified with the rectifier 4 and smoothed by the smoothing reactor 5 and the smoothing capacitor 8, and the direct-current power is supplied to the load 7.
However, the direct-current power supplies 10a to 10c and 11a to 11c are provided separately from a main circuit. Accordingly, it is not possible to supply the power of the direct current power supply 11a from the main circuit in a non-isolated manner when the alternating-current terminal 2b of the S phase is in the state of the lowest potential. For this reason, the direct-current power is supplied to the gate drive circuits 12a to 12c via an unillustrated separate isolated converter.
In other words, since it is necessary to use the separate isolated converter, the conventional configuration causes an increase in the number of components which leads to complication of the AC-DC converter device.